#include <cassert>
#include <functional>
#include <set>
#include <ctime>
#include <cmath>
#include <climits>
#include <cstring>
#include <string>
#include <queue>
#include <map>
#include <vector>
#include <algorithm>
#include <iostream>
#include <cstdio>
#ifndef ONLINE_JUDGE //POJ
# include <complex>
# include <random>
# include <array>
# define mkt make_tuple
# define empb emplace_back
#endif
#ifdef _LOCAL
# include "for_local.h"
#endif
using namespace std;
typedef unsigned int uint; typedef long long ll; typedef unsigned long long ull;
#define repi(_I, _B, _E) for(int _I = (_B); (_I) < (_E); ++ (_I))
#define rep(_I, _N) for(int _I = 0; (_I) < (_N); ++ (_I))
#define mkp make_pair
#define all(_X) (_X).begin(), (_X).end()


string src;

bool palindromize(int i, int ri, int cntInsert, int& pos, char& ch)
{
	while ( i <= ri ) {
		if ( src[i] != src[ri] ) {
			if ( cntInsert > 0 ) {
				if ( palindromize(i, ri - 1, cntInsert - 1, pos, ch) ) { pos = i; ch = src[ri]; return true; }
				if ( palindromize(i + 1, ri, cntInsert - 1, pos, ch) ) { pos = ri + 1; ch = src[i]; return true; }
			}
			return false;
		}
		++i;
		--ri;
	}
	if ( i > ri ) { pos = i; ch = 'a'; }
	return true;
}

signed main()
{
	cin >> src;

	int pos = string::npos;
	char ch = '\0';

	if ( palindromize(0, src.size() - 1, 1, pos, ch) ) {
		src.insert(pos, 1, ch);
		cout << src << endl;
	} else {
		cout << "NA" << endl;
	}
	return 0;
}